Comparative study of wetting patterns of drip emitters developed for microirrigation systems

Abstract

A research study was conducted to introduce two water saving emitters for surface and subsurface irrigation systems using low cost and freely available materials. Subsurface emitter has a special feature named textile interface which was used to increase the potential gradient between the textile interface and the soil matrix. Present study was conducted to estimate the soil volume wetted by each emitter. In order to compare the performances, commercially available surface drip emitter was also tested. Laboratory experiment was designed using a box having a transparent sheet o f glass fixed to one side o f the box to observe the wetting patterns. The design box was filled with soil to maintain the bulk density within the box at 1.3 g/cm for each and every test. Achievable minimum flow rates o f the newly developed surface and sub surface emitters were maintained as 11 cm3 m in1. Flow rate o f commercially available emitter was measured and achievable minimum flow rate was about 26.13 cm3 m in1. Time o f irrigation was fixed as 30 minutes for the three experiments. Applied amount o f water was measured in each irrigation and it was about 330 cm3 for surface and sub surface emitters. Amount o f water applied by the commercial emitter was about 783.9 cm3 during 30 min irrigation time period. Assuming that the volume and geometry o f the wetted soil under a point source is best represented by a truncated ellipsoid, wetted soil volumes were calculated. Maximum diameter o f the ellipsoid was measured and the distance to that level from the soil surface was also measured as a parameter which is required for the calculations. Vertical extent o f the soil volume was also measured. Time taken to achieve the maximum height and diameter was also quantified at the beginning o f the irrigation. The emitter having textile interface achieved 1648.8 cm3 o f wetted soil volume within 57 minutes and emitter which was used as a surface drip achieved 641.92 cm3 o f wetted soil volume within 40 minutes. Whereas commercially available surface drip emitter consumed 453.9 cm3 more water and achieved 3351 cm3 o f wetted soil volume within 55 minutes.